The present application relates generally to a heating ventilating and air conditioning (HVAC) system for a vehicle.
Conventional vehicle HVAC systems have a refrigeration circuit and a heating circuit. The conventional refrigeration circuit includes a compressor, which compresses the refrigerant and sends it through to a condenser, where heat is removed from the refrigerant. The refrigerant then flows through an expansion device, dropping the temperature further, before it enters an evaporator in an HVAC module of a passenger compartment. The evaporator absorbs heat from air flowing through it before the air flows into the passenger compartment. The refrigerant then flows from the evaporator back into the compressor to start the process over again. The conventional heating circuit employs a heater core in the HVAC module in the passenger compartment, where hot coolant from the engine cooling system flows through it to heat the air before it flows into the passenger compartment.
The refrigeration circuit has drawbacks in that, for refrigerant systems employing expansion valves and receiver dryers, storing the refrigerant above a critical charge by sub-cooling is required. The refrigerant storage occurs in the condenser, which increases the pressure drop in the system and thus reduces the condenser capacity. This results in reduced system efficiency.
The heating circuit has drawbacks in that the heater core cannot provide heat to the air flowing through it until the engine has time to warm up the coolant. This becomes even more of a concern as modern engines become more efficient, thus producing less excess heat to warm up the engine coolant. Electric powered heaters can be provided for supplemental heating while the coolant warms up. However, this electric heat may not be very energy-efficient and may further burden the vehicle electrical system that may be operating near its capacity in the first place.
Thus, it is desirable to provide an HVAC system for a vehicle that may provide heating or air conditioning in a more efficient or timely manner.